I've heard of many people (on this site, friends and acquaintances, posts on SM) who own now-restricted firearms that are planning on saying nothing and locking their guns up somewhere deep in their basement and not touching it unless they need it for the zombie apocalypse.
Imagine if they received an email directly to them (ie naming them by name, and not just a wide email blast to gun owners) that says basically "we know you have a restricted firearm, turn it in before October 30th or else face legal consequences". I wonder, amongst these people, how many would fess-up and turn their guns in and how many would continue to play quiet and hope it blows over.